Out of 108, a total of 52 donors have returned to the NIH for the follow-up protocol visit since 3/2009. All donors who have returned have reported that the kidney donation has been a positive experience. No one thus far has had expressed any sense of regret or concerns regarding care received at the NIH. In some donors, the experience of kidney donation has encouraged them to make healthy life style choices. In many we have thus seen, however, development of weight gain, hypertension, and hyperlipidemia has not been uncommon, as in the general population. We have nearly completed the measurements of cortical and total renal volume changes following nephrectomy in 52 patients. We will then investigate if there is any correlation between the renal cortical or total renal volume change and donor renal outcomes. The following abstract summarizes our analysis thus far. COMPREHENSIVE EVALUATION OF THE LIVING KIDNEY DONORS: A NIH EXPERIENCE Stefanie Glenn1, Xiongce Zhao2, Ann Sloane4, Kim Burks1, Liz Hale3, Michael Ring1, Noelle Dickey3, Monique E. Cho1 The National Institutes of Health, Bethesda, MD Although the available data suggest kidney donation is safe, controversy remains regarding long-term consequences of nephrectomy, particularly for older donors. Between 1999 and 2006, 108 patients have undergone kidney donation at the NIH. In order to obtain comprehensive clinical evaluation, all donors were invited to participate in a follow-up study. Out of 108, 52 donors returned to the NIH for clinical and laboratory exams and detailed interviews. For those who did not return, we reviewed available medical records. Our donors (n=108) were mostly Caucasian, with 14 African Americans and 51 males. The mean follow-up period was 43 years. Their baseline characteristics included mean(SD) age of 4111 yrs, BMI 275 kg/m2, CrCL 13128 mL/min, and BP 122/7212/10 mmHg. Of the 108, 51 donors had follow-up duration of &#8805;4 yrs and we limited our analysis to this group. Following a mean follow-up duration of 6.5 yrs, the significant changes in these 51 patients included 7% increase in BMI (P=0.0003);66% increase in proteinuria, from 126 mg to 185 mg/d (p=0.006);and a trend toward increased systolic blood pressure by 3% (P=0.06). Their serum Cr remained stable but persistently elevated following nephrectomy, from a baseline of 0.850.2 to 1.20.3 (P=0.0001). We also identified 13 patients (Case) whose creatinine nadir following nephrectomy persistently remained >50% from the baseline. When comparing the Case pts to the remaining 38 donors (Control), their latest serum Cr after a mean follow-up duration of 7 yrs was 1.410.3 mg/dL, compared to 1.10.2 mg/dL in the Control group (p=0.0006). The only significant difference between the Case and Control groups was higher baseline age in the Case (508 vs. 4110 yrs, P=0.01). While our study is limited by its small size and short duration, it underscores an important question whether older donors can compensate for nephrectomy as well as younger donors and if they may be at higher risk for worse long-term renal outcome.